How do I replay sidequests?

I'm running low on mana and I'd like to farm another rift ember or two. You can get the rift ember from a sidequest in the Ossean Wastes in act 2, but I've already done the quest and it doesn't seem to pop up again when I travel between acts then take the waypoint to act 2. Is there a way to replay sidequests in general, and specifically this sidequest?2 years ago